POPULATION-STRUCTURE IN MEDITERRANEAN ISLANDS AND RISK OF GENETIC INVASION IN CULEX-PIPIENS L (DIPTERA, CULICIDAE)

The mosquito Culex pipiens is subjected to organophosphate treatments in both Corsica and southern Sardinia, but the resistance gene A2-B2, which is currently in a worldwide expansion, has only reached Sardinia . In order to understand this situation, the genetic structure of popu lations sampled in Sardinia and Corsica was assessed using 15 isozymes . Two loci (HK1 and HK2) were not taken into account because of the po ssibility of selection. For the other loci, statistical independence w as not rejected for all possible pairs, and no deviation from Hardy-We inberg expectations was apparent. Low but significant genic differenti ation was present between Corsica and Sardinia, as well as between nor thern and southern Sardinia, despite a large number of effective migra nts per generation. These results are discussed in the context of the high probability of extinction/recolonization of breeding sites, the f light migration ability of this mosquito, and the pleiotropic cost of insecticide resistances genes. It is concluded that A2-B2 resistance i s unlikely to reach Corsica from southern Sardinia, unless accidental human transportation occurs. (C) 1995 The Linnean Society of London.